Most Americans today experience some form of periodontal disease, making it among the most common infectious diseases of adults and a significant public health burden. Combining exciting recent advances in nanotechnology and photodynamic therapy with what is being learned about the biofilms that make up dental plaque may provide a powerful new tool to combat this widespread, expensive, and often difficult-to-treat problem. [unreadable] [unreadable] Surface modified TiO2 nanoparticles are non-toxic, robust, and straight forward to manufacture, and exhibit remarkable inducible, photocatalytic properties, making them ideally suited for photodynamic therapy. Numerous clinical applications exist if these nanoparticles can be effectively targeted while retaining their photosensitizer activity. One such application is to selectively eradicate pathogenic elements in dental biofilms without adversely affecting the normal oral flora. [unreadable] [unreadable] This research will establish the feasibility of applying this approach to periodontal disease, by specifically targeting TiO2 nanoparticles to the pathogenic bacteria Porphyromonas gingivalis. Surface modified TiO2 will be chemically linked to select biochemical targeting moieties. The activity of these functionalized nanoparticles will be assessed under a wide range of photoactivation conditions. Selectivity for P.gingivalis over the common, non-pathogenic oral bacterium Streptococcus gordonii will be evaluated. Finally, the effect of surface modified, functionalized TiO2 nanoparticles on both targeted and non-targeted bacteria will be determined. .Such a demonstration-the effective targeting and selective destruction or inhibition of pathogenic subgroups within dental plaque biofilms-will be the first step towards developing photodynamic therapy into a commercially viable, clinically relevant treatment for periodontal disease. [unreadable] [unreadable]